2manytoys

iTrader: (9)

Can some one point me in the right direction. I have a set of PRC 5.3 heads shaved, Comp R lifters, and Comp adj rocker arms. How do I check for proper pushrod length? I know I will need a length checker but how do I determine when the proper length is achieved? And what about setting lifter preload? All help is appreciated.

vettenuts

iTrader: (4)

Here is how I did it. If the heads are still off the car it might be easier, if not you can still do it. With adjustable rockers, the pushrod length determines both wipe and preload. You need to figure wipe first. I did this by setting up a dial indicator and using it to measure the lift at the valve. Then install check springs and the rockers without pushrods or the set screw in the poly lock, only use the adjusting nut. You will need to rotate the rockers by hand by simultaneously pulling up against the adjusting nut and rotating through the valve lift as if the pushrod were doing the job. Once you get an acceptable wipe pattern, measure the depth on the adjusting nut from the top of the nut to the top of the stud. Try a few depths once you get a good wipe to see how much effect different depth measurements change the wipe such that you end up with a range of depth measurements that provide an acceptable wipe. The next step requires the heads are on the car, but basically you set the adjusting nut to your correct wipe depth and then measure for the pushrods. Since you are running Comp R's, just get the correct measurement as the preload is tiny on these so you won't have to do any further compensation. You will likely find that the depth setting give you an non-standard pushrod length, however if you know the acceptable range of depth measurements you should be able to make adjustments until you come up with a standard pushrod length.

I hope this all makes sense. Here's a couple of photo's to hopefully clear it up.

joshua022

iTrader: (12)

How much where the heads milled?? my PRC 2.5s were milled .045 (57cc)so I used 7.350 pushrods instead of the stock 7.4s

Z06PSI

iTrader: (33)

Did you just use a pry bar to depress the spring? Did you use the measured depth of the adjusting nut for all cylinders?

vettenuts

iTrader: (4)

No, check springs can be depressed by hand. I only did one cylinder. The final preload will be set by the adjustment method.

2manytoys

iTrader: (9)

I believe my heads are only milled .030. The heads are installed on the engine, but not in the car yet. This method sounds like it will work.